1. Field of the Invention
The present invention relates to a method and apparatus for adjusting the clock throttle rate of a central processing unit (CPU) included in a computer.
2. Background of the Related Art
A computer (or “system”) 4, as illustrated in FIG. 1A, is commonly used with external output devices, such as a display monitor 6 and a printer 12, as well as external input devices, such as a keyboard 8 and a mouse 10. The power management of a system 4 is often controlled by external input devices.
A power management method in the related art will be described in conjunction with FIG. 1 which illustrates a related method for managing the electric power consumed in a system. Once the system is turned on (Step S10), the system 4 determines whether a signal has been inputted from an external input device, such as a keyboard or mouse, to the system for a predetermined period of time (Step S11). If there is a signal inputted from the external input device within a predetermined period of time, the system is maintained in its ON state. On the other hand, if no signal is inputted from the external input device for the predetermined period of time, the system is switched from its ON state to an idle mode (Step S12) to reduce the electric power consumed in the system.
In systems where an advanced power management (APM) is applied, the operational mode when no signal is inputted from the external input device for a certain period of time is referred to as an “idle mode” or “doze mode”. When the system is switched to the “idle mode”, the basic input/output system (BIOS) of the system conducts an operation for reducing the clock speed supplied to the CPU and decreasing LCD brightness, etc., thereby reducing the consumption of electric power.
For instance, a dedicated power management chipset such as an Intel PIIX4E power management chipset is mainly used as a means for conducting the above mentioned APM power management operation. Typically, this power management chipset adjusts the clock throttle rate of the CPU among 7 different levels of 12.5%, 25%, 37.5%, 50%, 62.5%, 75%, and 87.5%. That is, assuming that the maximum speed of the CPU corresponds to 100%, the clock throttle rate of the CPU can be stepwise adjusted in a range from 100% to 12.5% at a reduction rate of 12.5% per step using the dedicated power management chipset (Intel PIIX4E).
In order to control the clock rate of the CPU, a clock throttle operation is also carried out by controlling desired registers of the power management chipset (Intel PIIX4E). A user controls desired registers to adjust the set-up of the BIOS to enable an idle mode supporting item and the clock rate of the CPU selects one of 7 different levels designated by the BIOS of the system, typically, 50%.
Meanwhile, in a system where an advanced configuration and power interface (ACPI) is applied and the system is in a state of use by an application program, the system sets the CPU at a clock throttle rate of 100% and the switching of the system to an “idle mode” by the BIOS of the system is not carried out. On the other hand, when the CPU is not being used by an application program, the system conducts a power management operation setting the CPU to a lower clock throttle rate.
However, the above mentioned power management methods of the related art have problems. In the case of the system to which the APM is applied, the clock throttle rate is reduced to a predetermined rate (typically, 50%) only when the system is switched from its ON state to an idle state. For this reason, there is a problem in that no power management is carried out in the ON state of the system.
Furthermore, although it is not necessary to use external input devices when operating a digital video disk (DVD) or a video file to allow the user to watch a movie or a program broadcasted on the Internet, the system should be in the ON state because the system remains in operation. In this case, however, the system may maintain or switch into the idle state because of a lack of external input by the user, thus resulting in slower or intermittent reproduction of the data.
In the case of the system to which the ACPI is applied, it is possible to conduct power management while the system is in the ON state. However, the power management is very simple, in that clocks are operated at a clock throttle rate of 100% in the operating state of the CPU, but the clocks are cut off in the non-operating state of the CPU. In accordance with such a very simple power management, clocks are supplied to the CPU at a maximum clock throttle rate even in a situation in which an application program involving a less CPU usage is used. For this reason, an increased consumption of electric power occurs unnecessarily in the system.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.